Apomixis, the asexual formation of seeds, holds revolutionary potential for fixing hybrid vigor in crops. For decades, research in this field has been dominated by a gene-centric view that focuses on identifying key regulators of apomeiosis and parthenogenesis. Although this strategy has achieved notable success in rice (Oryza sativa), it fails to explain several fundamental aspects of apomixis such as its strong association with polyploidy and interspecific hybridization, its facultative nature, and the localization of apomixis control regions within dense heterochromatin. Here, we propose a new framework that conceptualizes apomixis primarily as an epigenetic phenomenon, where its initiation is driven not by the acquisition of a new function but by the loss of epigenetic suppression that normally maintains the developmental barrier between somatic and reproductive cell fates. Furthermore, this framework integrates environmental cues mediated by reactive oxygen species as external triggers that induce epigenetic modulation regulating the penetrance of apomixis. Consequent, we re-evaluated the genetic basis of apomixis from an epigenetic perspective, redefining key genes as downstream effectors that were unlocked by upstream epigenetic events such as chromatin-level silencing, histone modifications, and post-transcriptional silencing. We concluded that understanding and manipulating this epigenetic switch governing the somatic-to-reproductive transition was the true key to achieving synthetic apomixis in diverse crops.

Soil salinization and phosphorus deficiency are the "double bottlenecks" that limit the yield of alfalfa in the Yellow River Basin. In the irrigation areas of the Yellow River Basin, the accumulation of soil salts driven by evaporation and the insufficient biological availability of phosphorus combine, further exacerbating the contradiction between water and soil resource utilization and restricting the sustainable development of forage industries on saline-alkali marginal lands. The use of salt-tolerant phosphorus-decomposing bacteria (ST-PSB) is a promising restoration strategy; however, traditional screening methods often ignore the community assembly patterns in the native habitat, resulting in low colonization efficiency of the strains and greatly restricting the practical application effect of the microbial agents. To break through the barrier between microbial ecological theory and the practice of saline-alkali soil improvement, this study established a new screening framework based on the theory of community assembly. Using high-throughput sequencing and neutral community model (NCM), soil samples from six typical saline-alkali areas in the Yellow River Basin (such as Beigutan Village and Dapao Village) were analyzed to determine the core taxonomic groups. Subsequently, functional strains were isolated and their regulatory effects on the growth of alfalfa under salt stress conditions were verified. The results demonstrated that: (1) The composition of soil microbial communities varies significantly in different regions (PC1/PC2 explained 29.41% of variation), yet community assembly was predominantly governed by stochastic processes (NCM R²=53.37%). Within this stochastic framework, Bacillus was identified as a persistent, core genus adaptable to broad environmental gradients. (2) Guided by these ecological insights, 40 Bacillus strains were isolated. Strain 16213 exhibited the highest IAA secretion (15.13 mg/L), while strain 14343 had the highest extracellular polysaccharide production (64.91 mg/L). Strain 14312 demonstrated superior phosphorus-solubilizing capacity (peaking at 96 h), with activity inversely correlated with salinity. (3) Pot experiments revealed that the consortium treatment J200 (Inoculated strain + 200 mmol/L NaCl) outperformed the control and other groups, exhibiting optimal root development and biomass accumulation. This study has confirmed that the core species (such as Bacillus) identified through the establishment of a new screening framework can optimize the rhizosphere microenvironment of alfalfa, thereby deepening the basic theoretical understanding of the restoration strategy for high-quality germplasm. The identified J200 strain can provide important microbial genetic resources for soil and water improvement, ecological restoration, and sustainable cultivation of alfalfa in the Yellow River Basin.

Global climate change has exacerbated drought stress episodes, which are emerging as a serious threat to plant growth and productivity worldwide. In this context, melatonin has emerged as a potential signaling molecule for improved drought tolerance in plants, primarily through enhanced antioxidant defenses. Here, physiological, transcriptome, and metabolome analyses were used to investigate the physiological and molecular mechanisms of melatonin in drought stress mitigation in A. mongolicum with both drought-tolerant and drought-sensitive genotypes. Physiological results suggest that melatonin improves drought tolerance in A. mongolicum primarily by enhancing the antioxidant enzyme system. Integrated transcriptomic and metabolomic analyses have demonstrated that the tryptophan metabolic pathway plays a crucial role in melatonin-mediated enhancement of drought resistance. Notably, we report on the drought-related gene AmASMT, which encodes a melatonin biosynthesis enzyme and contributes to drought stress tolerance in A. mongolicum. We found that the AmASMT overexpressing rice lines exhibited higher endogenous melatonin levels and increased tolerance to drought stress by promoting antioxidant systems. Our findings indicate that the AmASMT plays a crucial role in regulating melatonin biosynthesis A. mongolicum while facilitating protection against drought stress. These results shed light on the regulatory mechanism of melatonin biosynthesis related to the drought stress response A. mongolicum, and provides a basis for exploiting melatonin-mediated mechanisms and genetic engineering approaches to enhance plant drought tolerance.

Introduction:Exploiting photovoltaic power generation as a novel source of clean energy has become increasingly common in recent times. Nevertheless, the impact of photovoltaic power plants (PVs) on soil microbial activity and several functions is unclear. Methods:The present investigation aims to collect soil samples from photovoltaic power plants in arid and semi-arid regions with different years of construction, determine the physicochemical properties of the soil, and employ high-throughput sequencing to obtain 16S rRNA and ITS genes from the PV. This approach examines the community composition of bacteria and fungi in plant soils. This dataset is adopted to explore the role of soil physicochemical characteristics and climatic factors in the variousness and complexness of the network of soil microbial communities in PVs. Results:The findings reveal that soil physicochemical properties exhibit a gradual increase over time, with bacterial and fungal diversity showing a corresponding gradual increase and reaching a maximum over a period of 5-10 years. Furthermore, it is observed that the topological properties of the microbial network underwent significant changes driven by microbial diversity. Bacterial and fungal diversity as well as network complexity also display positive and negative correlations, respectively. A positive and significant correlation is detected between the bacterial network complexity and the soil multifunctionality, whereas a substantial negative correlation is observed between the fungal network complexity and the soil multifunctionality. Discussion:In conclusion the environment is able to directly regulate soil microbial diversity, thereby affecting network complexity and driving soil multifunctionality. Such discoveries are aimed to have crucial ecological implications for predicting environmental-soil-microbial effects on soil multifunctionality in photovoltaic zones.

Salt stress has become a significant constraint on agricultural yield and plant development. Melatonin (MT) and calcium (Ca2 +) are well recognized as key elements in salt-stress resistance in plants. In spite of this, the underlying mechanisms governing the effects of MT and Ca2+ interplay on alfalfa (Medicago sativa L.) salt tolerance remain a mystery. This research sought to investigate the regulatory mechanisms of MT and Ca2+ in alfalfa salinity response through physiological and comparative transcriptome. Physiological results indicated that exogenous MT and CaCl2 alleviated salinity stress-induced damage to alfalfa, which was reflected by increased plant growth parameters, Ca2+ in the cytosol ([Ca2+]cyt), antioxidant enzyme activities, K+/Na+ ratio, endogenous MT content, and decreased of electrolyte leakage (EL) and superoxide anion (O2 center dot-) levels, especially when they were applied simultaneously. Transcriptome analysis suggested that MT and Ca2+ mainly regulated genes related to Ca2+ signal transduction, hormone signal transduction, photosynthesis, reactive oxygen species (ROS) metabolism and ion transport to mediate salt stress in alfalfa. Additionally, transcription factor (TF) families like ERF, bHLH, WRKY, and NAC were also active in salt stress response mediated by MT and Ca2+. Moreover, nine hub genes were identified by weighted gene co-expression network analysis (WGCNA). Overall, this research revealed that MT and Ca2+ exert a synergistic influence on the regulation of salinity resistance, offering valuable insights for the development of salt-tolerant alfalfa varieties.

Drought is a major natural disaster that affects plant growth. Agropyron mongolicum possesses a wide range of drought tolerance genes acquired during its long evolution and adaptation to harsh environments. However, the regulatory mechanisms for drought resistance in A. mongolicum are complex, limiting the development and utilization of gene resources in response to drought stress. In this study, we examined differences in morphological, physiological, metabolite and transcript levels between the drought-tolerant (T) and drought-sensitive (S) genotypes of A. mongolicum to identify key metabolites and genes associated with the drought response. The morphological and physiological results suggest that the S genotype is suppressed by drought stress to a greater extent than the T genotype. Based on the metabolome and transcriptome data, we identified that serine/threonine-protein kinase SRK2 (SRK2), peptide chain release factor subunit 1 (eRF1), glutamine synthetase (GS), polyphenol oxidase (PPO), and aspartyl protease family protein (ASP) were highly correlated with key metabolites such as L-γ-glutamyl-L-leucine and γ-glutamylphenylalanine in leaves by co-expression network analysis, and alcohol-forming fatty acyl-CoA reductase (FAR), DNA oxidative demethylase (ALKBH), GDSL esterase/lipase (GELP), beta-fructofuranosidase (INV), and glutamine synthetase (GS) were highly correlated with key metabolites such as Trp-Glu-Ile and citric acid diglucoside in roots. Moreover, we identified the potential involvement of fatty acid degradation and glycolysis/glucogenesis pathways in the enhancement of drought tolerance in A. mongolicum. This study provides a foundation for genetic engineering studies of drought resistance in Poaceae plants. Key metabolites and genes associated with drought response were identified by analyzing the morphology, physiology, metabolites, and genes of the drought-tolerant and drought-sensitive genotypes of Agropyron mongolicum leaves and roots.

Drought is one of the most devastating abiotic stresses worldwide, threatening global agricultural productivity. As a critical species for ecological restoration of degraded grasslands in arid regions, Agropyron mongolicum requires enhanced drought tolerance to ensure successful revegetation under water-limited conditions. In this context, melatonin has emerged as a pleiotropic regulatory molecule that orchestrates complex regulatory networks to enhance plant drought tolerance. Here, we integrated physiological and transcriptomic analyses to elucidate how melatonin alleviates drought stress in A. mongolicum by regulating carbon and nitrogen metabolism in both leaves and roots, thereby enhancing drought tolerance. Our results showed that drought stress significantly inhibited A. mongolicum seedling growth, while exogenous melatonin application alleviated these effects by increasing biomass accumulation, reducing lipid peroxidation, enhancing antioxidant enzyme activity, and promoting endogenous melatonin and osmolyte accumulation. RNA-Seq analysis indicated melatonin-responsive genes were significantly enriched in carbon and nitrogen metabolic pathways under drought conditions. Comprehensive analysis of transcriptomic, enzymatic, and metabolite data further demonstrated that melatonin treatment maintained a more active and balanced carbon and nitrogen metabolic homeostasis, particularly evident in enhanced sucrose biosynthesis and improved nitrogen assimilation efficiency under drought stress. Overall, our findings elucidate the mechanistic basis by which melatonin coordinates carbon and nitrogen metabolic networks to enhance drought tolerance in A. mongolicum, providing valuable insights for harnessing melatonin as a sustainable strategy to improve plant drought resistance.

IntroductionSalt stress significantly affects plant growth, and Na+ has gained attention for its potential to enhance plant adaptability to saline conditions. However, the interactions between Na+, plants, and rhizosphere bacterial communities remain unclear, hindering a deeper understanding of how Na+ contributes to plant resilience under salt stress.MethodsThis study aimed to investigate the mechanisms through which Na+ promotes alfalfa's adaptation to salt stress by modifying rhizosphere bacterial communities. We examined the metabolic activity and community composition of both plant and rhizosphere bacteria under Na+ treatment.Results and discussionOur results revealed significant changes in the metabolism and community composition of both plant and rhizosphere bacteria following Na+ addition. Na+ not only promoted the growth of rhizosphere bacteria but also induced shifts in the plant-associated bacterial community, increasing the abundance of bacterial species linked to alfalfa's resistance to salt stress. Furthermore, the chemical characteristics of alfalfa were strongly correlated with the composition and network complexity of both plant and rhizosphere bacterial communities. These interactions suggest that Na+ plays a crucial role in enhancing alfalfa’s adaptability to salt stress by fostering beneficial bacterial communities in the rhizosphere. This finding highlights the potential of leveraging Na+ interactions with plant-microbe systems to improve crop resilience and productivity in saline agricultural environments.

The key to restoring arid and semi-arid ecosystems is maintaining soil water and organic carbon contents. Alfalfa (Medicago sativa L.) is a high-yield perennial forage crop and performs ecological functions as a drought-resistance leguminous herb. It has been widely planted for reconstruction of degraded soils in the Loess Plateau in northwestern China, but long-term planting may affect soil carbon-water coupling and lead to crop yield reduction. To maximize the benefits of reconstructed grassland, this study explored the couplings of soil water, organic carbon, and alfalfa productivity along a reconstruction chronosequence in a semi-arid area of the Loess Plateau. Spacefor-time substitution approach was used to select different-aged stands of reconstructed grassland (1, 5, 7, 10, 15, 20, 30 years old). Alfalfa above-ground biomass (AGB), soil water storage (SWS), organic carbon storage (SOCS), and carbon-water coupling coordination degree (D) were measured in the 0-100 cm soil profile. Alfalfa AGB reached a peak in the 7th year, and the degradation began in the 10th year. Both SWS and SOCS varied nonlinearly with stand age. The greatest loss of SWS occurred in the 15th year (80-100 cm depth), whereas the largest increase of SOCS occurred in the 30th year (0-20 cm depth). There was a negative feedback relationship between AGB and SWS over the 30-year study period (Pearson r = -0.835, P = 0.098). AGB and SOCS initially showed a trade-off within the first 10 years (Pearson r = -0.7431, P = 0.2569), in contrast to their positive feedback in the 20-30th years (Pearson r = 0.9978, P = 0.0421). A decoupling between SWS and SOCS (D < 0.6) was observed after 12 years of alfalfa planting. For agricultural production, a greater supply of water and organic fertilizer is required from the 7th year of alfalfa planting, and reseeding may be needed around the 10th year to prolong the life of alfalfa community. Alfalfa should be planted for no more than 12 consecutive years in the study area for ecological protection.

Alfalfa (Medicago sativa L.) establishment is an effective strategy for grassland reconstruction in degraded ecosystems. However, the mechanisms underlying vegetation succession in reconstructed grasslands following alfalfa establishment remain elusive. In this study, we investigated vegetation community, soil quality and rhizosphere microbiota dynamics across a reconstructed grassland chronosequence in the loess region of Northwest China. A space-for-time substitution method was used to evaluate grassland vegetation coverage and alfalfa production performance in nine stands of different ages (1-50 years old). High-throughput sequencing was conducted to characterise rhizosphere microbial communities associated with alfalfa. The plant heights, yields and stem-to-leaf ratios of alfalfa all peaked in the 7-year-old stand and then decreased in older stands, with Stipa bungeana replacing alfalfa as the dominant species in the 50-year-old stand. Soil bulk density and major nutrient contents were highest in the artificial grassland (1-10 years). Soil enzyme activities (e.g., urease and sucrase) were enhanced in the transitional grassland (10-30 years), accompanied by enrichment of potentially beneficial microbial taxa (e.g., Actinobacteria and Mortierella) and functional fungi (e.g., saprotrophs and symbiotrophs) in the rhizosphere. Soil water content, total porosity and rhizosphere microbial diversity reached their maximum levels in the natural grassland (>30 years). The results indicate that alfalfa establishment alters soil structure and nutrient status in the short term, creating an optimal rhizosphere micro-environment. The improved soil conditions and rhizosphere microbiota are favourable for subsequent establishment of native grass species, leading to the formation of a stable semi-natural grasslands.

Background B-box (BBX) family is a class of zinc finger transcription factors (TFs) that play essential roles in regulating plant growth, development, as well as abiotic stress. However, no systematic analysis of BBX genes has yet been conducted in alfalfa ( Medica go sativa L.), and their functions have not been elucidated up to now. Results In this study, 28 MsBBX genes were identified from the alfalfa genome, which were clustered into 4 subfamilies according to an evolutionary tree of BBX proteins. Exon-intron structure and conserved motif analysis reflected the evolutionary conservation of MsBBXs in alfalfa. Collinearity analysis showed that segmental duplication promoted the expansion of the MsBBX family. Analysis of cis -regulatory elements suggested that the MsBBX genes possessed many growth/development-, light-, phytohormone-, and abiotic stress-related elements. MsBBX genes were differentially expressed in leaves, flowers, pre-elongated stems, elongated stems, roots and nodules, and most MsBBX s were remarkably induced by drought, salt and various plant growth regulators (ABA, JA, and SA). Further functional verification demonstrated that overexpressing of the MsBBX11 gene clearly promoted salt tolerance in transgenic Arabidopsis by regulating growth and physiological processes of seedlings. Conclusions This research provides insights into further functional research and regulatory mechanisms of MsBBX family genes under abiotic stress of alfalfa.

Auxin/induced-3-acetic acid (Aux/IAA) is an important plant hormone that affects plant growth and resistance to abiotic stresses. Drought stress is a vital factor in reducing plant biomass yield and production quality. Alfalfa (Medicago sativa L.) is the most widely planted leguminous forage and one of the most economically valuable crops in the world. Aux/IAA is one of the early responsive gene families of auxin, playing a crucial role in response to drought stress. However, the characteristics of the Aux/IAA gene family in alfalfa and its potential function in response to drought stress are still unknown. A total of 41 Aux/IAA gene members were identified in alfalfa genome. The physicochemical, peptide structure, secondary and tertiary structure analysis of proteins encoded by these genes revealed functional diversity of the MsIAA gene. A phylogenetic analysis classified the MsIAA genes into I-X classes in two subgroups. And according to the gene domain structure, these genes were classified into typical MsIAA and atypical MsIAA. Gene structure analysis showed that the MsIAA genes contained 1–4 related motifs, and except for the third chromosome without MsIAAs, they were all located on 7 chromosomes. The gene duplication analysis revealed that segmental duplication and tandem duplication greatly affected the amplification of the MsIAA genes. Analysis of the Ka/Ks ratio of duplicated MsAux/IAA genes suggested purification selection pressure was high and functional differences were limited. In addition, identification and classification of promoter cis-elements elucidated that MsIAA genes contained numerous elements associated to phytohormone response and abiotic stress response. The prediction protein–protein interaction network showed that there was a complex interaction between the MsAux/IAA genes. Gene expression profiles were tissue-specific, and MsAux/IAA had a broad response to both common abiotic stress (ABA, salt, drought and cold) and heavy metal stress (Al and Pb). Furthermore, the expression patterns analysis of 41 Aux/IAA genes by the quantitative reverse transcription polymerase chain reaction (qRT-PCR) showed that Aux/IAA genes can act as positive or negative factors to regulate the drought resistance in alfalfa. This study provides useful information for the alfalfa auxin signaling gene families and candidate evidence for further investigation on the role of Aux/IAA under drought stress. Future studies could further elucidate the functional mechanism of the MsIAA genes response to drought stress.

The growth and biological decline of alfalfa may be linked to the rhizosphere microbiome. However, plant–microbe interactions in the rhizosphere of alfalfa and associated microbial community variations with stand age remain elusive. This study explored the successional pattern of rhizosphere microbial communities across different aged alfalfa stands and its relationship with alfalfa decline. Rhizosphere soils were collected from 2- and 6-year-old alfalfa stands. Control soils were collected from interspaces between alfalfa plants in the same stands. Soil bacterial and fungal communities were characterized by 16S and ITS rRNA gene sequencing, respectively. Specific microbial taxa colonized the rhizosphere soils, but not the control soils. The rhizosphere-specific taxa mainly included potentially beneficial genera (e.g., Dechloromonas, Verrucomicrobium) in the young stand and harmful genera (e.g., Peziza, Campylocarpon) in the old stand. Alfalfa roots regulated soil microbial communities by selective promotion or inhibition of distinct taxa. The majority of time-enriched taxa were reported as harmful fungi, whose relative abundances were negatively correlated with plant traits. Time-depleted taxa were mostly known as beneficial bacteria, which had relative abundances positively correlated with plant traits. The relative abundances of functional bacterial genes associated with vancomycin biosynthesis, zeatin biosynthesis, and amino acid metabolism trended lower in rhizosphere soils from the old stand. An upward trend was observed for fungal pathogens and wood saprotrophs with increasing stand age. The results suggest that root activity drives the negative succession of rhizosphere microbial communities during alfalfa decline in old stands.

Soil salinization, which severely limits crop yield and quality, has become a global environmental and resource issue. Melatonin plays an important role in plant responses to salt stress. Smooth bromegrass is an important forage with excellent feed value and is widely grown in northern and north-west China for pasture and sand binding. However, the physiological and molecular mechanisms underlying exogenous melatonin regulation of salt stress in smooth bromegrass are not clear. This study compared the phenotype, physiological, transcriptome, and metabolome profiles of two varieties with contrasting salt tolerance attributes under salt and melatonin treatment. After melatonin treatment, the catalase (CAT) and ascorbate peroxidase (APX) activity, proline content, actual photochemical efficiency (Y(II)), relative water content, and fresh weight above ground were significantly higher than under salt treatment, while relative conductivity, H2O2 content, and Na+/K+ ratio were significantly lower than salt treatment. The transcriptome and metabolite profiling analysis of smooth bromegrass seedlings treated without melatonin under salt stress identified the presence of 22522 differentially expressed genes (DEGs) and 862 differentially expressed metabolites (DEMs) in SS, 17809 DEGs and 812 DEMs in ST, while treated with melatonin under salt stress identified the presence of 7033 DEGs and 177 DEMs in SS, 2951 DEGs and 545 DEMs in ST. Furthermore, in response to salt stress, melatonin may be involved in regulating the correlation between DEGs and DEMs in flavonoid biosynthesis, proline biosynthesis, and melatonin biosynthesis. Moreover, melatonin participated in mediating melatonin biosynthesis pathways and affected the expression of ASMT in response to salt stress.

为探究干旱半干旱区沙芦草(Agropyron mongolicum)种子生产适宜的行距和播量配比,本试验采用双因素裂区试验设计,分别设4个行距水平(20,30,40,50 cm)和4个播量水平(10,15,20,25 kg·hm-2),研究了不同行距和播量配比对沙芦草种子产量及产量构成因子的影响.结果表明,行距对沙芦草实际种子产量和理论种子产量有极显著影响(P＜0.01),播量对沙芦草实际种子产量有显著影响(P＜0.05),行距和播量对沙芦草实际种子产量有极显著的正交互作用(P＜0.01).通径分析表明,小穗数、小花数、种子数、穗长和生殖枝数对种子产量的影响具有直接作用,对种子产量贡献最大的是生殖枝数;回归寻优模型分析得出,当行距为20 cm,播量为15 kg·hm-2时实际种子产量最高.因此,在宁夏中部干旱区沙芦草种子生产中建议种植密度应为行距为20 cm,播量为15 kg·hm-2 最佳.

Soil salinity is a major factor threatening the production of crops around the world. Smooth bromegrass (Bromus inermis L.) is a high-quality grass in northern and northwestern China. Currently, selecting and utilizing salt-tolerant genotypes is an important way to mitigate the detrimental effects of salinity on crop productivity. In our research, salt-tolerant and salt-sensitive varieties were selected from 57 accessions based on a comprehensive evaluation of 22 relevant indexes, and their salt-tolerance physiological and molecular mechanisms were further analyzed. Results showed significant differences in salt tolerance between 57 genotypes, with Q25 and Q46 considered to be the most salt-tolerant and salt-sensitive accessions, respectively, compared to other varieties. Under saline conditions, the salt-tolerant genotype Q25 not only maintained significantly higher photosynthetic performance, leaf relative water content (RWC), and proline content but also exhibited obviously lower relative conductivity and malondialdehyde (MDA) content than the salt-sensitive Q46 (p < 0.05). The transcriptome sequencing indicated 15,128 differentially expressed genes (DEGs) in Q46, of which 7,885 were upregulated and 7,243 downregulated, and 12,658 DEGs in Q25, of which 6,059 were upregulated and 6,599 downregulated. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the salt response differences between Q25 and Q46 were attributed to the variable expression of genes associated with plant hormone signal transduction and MAPK signaling pathways. Furthermore, a large number of candidate genes, related to salt tolerance, were detected, which involved transcription factors (zinc finger proteins) and accumulation of compatible osmolytes (glutathione S-transferases and pyrroline-5-carboxylate reductases), etc. This study offers an important view of the physiological and molecular regulatory mechanisms of salt tolerance in two smooth bromegrass genotypes and lays the foundation for further identification of key genes linked to salt tolerance.

为了研究株距和行距对宁夏干旱区苜蓿种子产量及构成因素的影响,以苜蓿品种"甘农4号"(Medicago sativa cv.Gannong No.4)作为试验材料,于2017～2020年连续4年采用再裂区试验设计,主区为行距(60、80和100 cm),裂区为株距(15、25和35 cm),再裂区为生长年份(2017、2018、2019和2020年),运用PCA主成分分析进行综合评价,确定苜蓿最优的株行距配比.结果表明,随着株距和行距的增加,苜蓿单株种子产量呈增加趋势.行距对每花序小花数、单株花序数、每荚种子数、单株种子产量以及单位面积种子产量均有极显著影响(P<0.01);株距对单株花序数、生殖枝数和每荚种子数以及单株和单位面积种子产量均有极显著影响(P<0.01);生长年份对产量构成因素及种子产量均有极显著影响;行距和株距相互作用对种子产量及其构成因素有显著或极显著作用;经通径分析得出,影响种子产量的主要因素是每花序结荚数、单株花序数和千粒重以及每荚种子数.回归最优模型得出,行距为100 cm,株距为 35 cm时,单株种子产量最高,为 27.910 kg/hm2,株距为 15 cm,行距为 100 cm时,单位面积种子产量最高,为1545.088 kg/hm2.因此,宁夏干旱区进行苜蓿种子生产时,株距15 cm,行距为100 cm为最佳配比.

【Objective】 This study investigated the characteristics of different Elymus dahuricus germplasms to screen elite germplasm materials of E. dahuricus.【Method】 A total of 21 E. dahuricus germplasms from different sources were selected and 17 agronomic indicators were measured to study the variations of main agronomic characters of E. dahuricus through statistical analysis such as correlation, principal component, multiple stepwise regression, and clustering.The main factors influencing yield formation of E. dahuricus were clarified.【Result】 The variations of agronomic characters of E. dahuricus were rich, and the coefficients of variation ranged from 11.07%（inflorescence length） to 45.53%（basal stem length）.Correlation analysis showed that hay yield per plant had significantly positive correlation with ba-sal stem length and flag leaf length（P＜0.05）,and seed yield per plant had significantly positive correlation with tiller number and thousand-grain weight（P＜0.01）.Multiple stepwise regression and path analysis showed that plant height, stem diameter, basal stem length, stem length under panicle, flag leaf width, length of the second leaf, sheath length of the second leaf, width of the second leaf, inflorescence length, spikelet length, and stem-to-leaf ratio were the main factors affecting the hay yield per plant, among which stem diameter, base stem length, under-ear stem length, flag leaf width, leaf sheath length, spikelet length, and stem-leaf ratio had direct contributions.Plant height, length of the second leaf sheath, length of the spikelet, number of tillers and thousand-grain weight were the main factors affecting seed yield per plant, among which length of spikelet and number of tillers had direct effects.The principal component analysis showed that the cumulative contribution rate of the first five principal components reached 79.304%. According to the first and second main components, Seven E. dahuricus germplasm materials of PJC09,PJC14,PJC15,PJC17,PJC18,PJC26,and PJC27 with high hay yield and seed yield per plant were screened.The average hay yield per plant was 197.02 g, and the seed yield per plant was 21.39 g.Cluster analysis showed that 21 accessions of E. dahuricus germplasm were clustered into 3 categories: category Ⅰ contained 2 germplasms for screening high seed yield per plant, category Ⅱ included 10 germplasms for screening high hay yield and seed yield per plant, category Ⅲ contained 9 germplasm materials for screening specific germplasm according to breeding goal.【Conclusion】 This study determined 11 main factors affecting hay yield per plant and 5 main factors affecting seed yield per plant.Seven E. dahuricus germplasm materials with excellent hay yield per plant and seed yield per plant were also screened.

Alfalfa is an important forage crop. Yield and quality are frequently threatened by extreme environments such as drought and salt stress. As a component of the cell wall, lignin plays an important role in the abiotic stress response, the mechanisms of which have not been well clarified. In this study, we combined physiological, transcriptional, and metabolic analyses to reveal the changes in lignin content in alfalfa under mannitol-induced osmotic stress. Osmotic stress enhanced lignin accumulation by increasing G and S units, which was associated with increases in enzyme activities and decreases in 8 intermediate metabolites. Upon combined analysis of the transcriptome and metabolome, we identified five key structural genes and several coexpressed transcription factors, such as MYB and WRKY, which may play a core role in regulating lignin content and composition under osmotic stress. In addition, lignin synthesis was positively regulated by ABA but negatively regulated by ethylene under osmotic stress. These results provide new insight into the regulatory mechanism of lignin synthesis under abiotic stress.

为探明宁夏苜蓿耐旱新品系'新盐 52号'(XY52)的miRNA表达谱,并筛选有跨界研究价值的microRNA(miR),以'中苜一号'(ZM1)为参照,对ZM1和XY52进行高通量miRs组学测序和分析(RNA-seq);通过生物信息学技术筛选差异表达miRs及预测靶基因,并对预测靶基因进行GO和KEGG富集分析;然后运用RT-qPCR技术对10个miRs进行检测和分析.结果表明,①成功构建了2种苜蓿miR表达谱,ZM1和XY52中分别检测到656和703个miRs,其中已知miRs分别为433和480个,新预测miRs数量均为233个;②2种苜蓿中共检测到21个差异表达miRs,其中novel-miR54、miR156f和miR166a表达量较高,并且novel-miR54在XY52中表达量极显著高于ZM1(P<0.01),miR156f在ZM1中的表达量极显著高于XY52(P<0.01);③5个已知有跨界调控功能miRs中,miR166a在ZM1和XY52中均为表达水平最高的miR;品种之间,miR166a在XY52中的表达量较ZM1极显著上调(P<0.01);④KEGG通路和GO功能富集分析发现差异表达的21个miRs共预测得到623个靶基因,主要与RNA转运、ABC转运蛋白和泛素介导的蛋白水解等信号通路有密切关系.以上结果为解析苜蓿品种miRs差异表达及研究苜蓿源miRs调控奶牛体内基因奠定初步基础.